1. Field of the Invention.
The present invention relates to a housing for a particle flow-through apparatus which includes a particle unclogging feature, and more particularly, concerns a flow cytometry apparatus for determining one or more characteristics of particles flowing through such a housing wherein clogged particles may be removed to facilitate operation of the apparatus.
2. Description of the Prior Art.
There are a number of cell or particle analyzing devices employing flow cytometry techniques which rely on hydrodynamically focused fluid flow through an aperture or orifice for determining specific characteristics of the flowing cells or particles. Flow analysis of particles has been employed in the determination of the variety of characteristics of individual particles. This analysis is most useful in analyzing or determining characteristics of cells for the collection information which would be useful in areas of research, hematology, immunology and the like. The researcher, for example, may be interested in determining specific characteristics of the individual cells so that such cells may be classified, identified, quantified and perhaps sorted for further investigations or analysis.
One commercially available flow cytometry apparatus which relies on a hydrodynamically focused fluid flow system is known as the FACS.TM. Analyzer sold by the FACS Systems Division of Becton, Dickinson and Company, Mt. View, Calif. The FACS Analyzer rapidly analyzes cells on the basis of fluorescence and electronic volume properties. Analysis is accomplished by introducing cells in suspension to the center of a focused liquid stream and causing them to pass, one at a time, through a filtered and focused light from a high power mercury arc lamp. Each cell is individually characterized by its electronic impedance volume and by the intensity and color of fluorescence emitted while it is illuminated. This analyzer is described in European Pat. No. 0068404. In the aforementioned flow cytometry apparatus, a sheath fluid is utilized to focus the particles or cells as they pass through the orifice associated with the analyzing or counting capabilities. U.S. Pat. Nos. 4,503,385 and 4,526,276 describe particle analysis systems in which particles flowing in a stream are enveloped in a sheath fluid which focuses and confines the sample fluid (with particles or cells) to the center of the flowing stream.
One of the problems which arises when using sheath flow in a hydrodynamically focused fluid system, particularly through a flowcell or flow chamber, is particle clogging. Inasmuch as the particles, such as cells, to be analyzed are typically in the order of 5 to 20 microns in size, the orifice through which these particles pass is very small, especially since the orifice is intended to allow the passage of only one particle at a time. If the sample fluid which contains the particles has cellular debris or particles of irregular size, passage of these materials toward the orifice of the flowcell could cause clogging problems.
In the presently known and available particle flow-through apparatuses, electrically operated high pressure pumps or the like are employed in the fluidics of the system to clean the liquid flow paths including the flowcell orifice and passageways for the particles to be analyzed. The usual operation for these high pressure pumps is to pass cleansing fluid in a direction reverse to the normal particle flow through the apparatus. However, if the particles or debris which clogged the flowcell orifice are clumped together or stuck in a difficult to clean position, the high pressures generated by the electrically operated pump are sometimes not sufficient to expel the debris. If the reverse flow pump does not unclog the orifice, it is usually necessary to take the apparatus apart to clean the individual elements. Reassembly usually requires readjustment and recalibration of optical and electronic elements of the system.
With the foregoing in mind, improved techniques for unclogging passageways in particle flow-through apparatuses are still being sought. Such improvements in a particle unclogging feature should preferably be included in the particle flow-through apparatus so that the various parts of the apparatus do not have to be disassemble din order to unclog the passageways. It is toward such an improvement that the present invention is directed.